A conventional end-face-emitting photonic crystal laser element is one forming an n-type cladding layer, an active layer, a diffraction grating layer (photonic crystal layer), and a p-type cladding layer in sequence on a semiconductor substrate and arranging drive electrodes on the upper and lower faces of thus formed substrate, respectively. Their semiconductor materials are those based on AlGaAs and can change their refractive indexes and energy bandgaps by altering their composition ratios of Al. Assuming that X, Y, and Z axes lie in the thickness, longitudinal, and width directions of the substrate, respectively, the upper-face electrode is elongated along the Z axis. Both end faces perpendicular to the Z axis are provided with non-reflective and high-reflective coatings, respectively. Even without the high-reflective coating, the semiconductors have a refractive index higher than that of air (=1), whereby light generated therein tends to be confined within the semiconductors.
Light generated in the active layer also exists in the photonic crystal layer and produces a two-dimensional resonant state under the influence of diffraction by the photonic crystal layer. A part of the light in the two-dimensional resonant state is taken out as optical output from the end face provided with the non-reflective coating. Unlike typical Fabry-Perot lasers, modes are also defined in ±Y and ±Z directions under the effect of the photonic crystal, whereby a broad-area, single transverse and longitudinal mode semiconductor laser can be attained.